“BlackJet,” a new app for iPhones, lists space-sharing opportunities in private jets. At present, it is available in ten major cities. Check the list at their web site, BlackJet.com. You need an invitation code to search for seats, but that’s easy to get. Enter the code “COOLBLACKJET100” at Blackjet.com. Unfortunately, there’s a membership fee of $2500; seats tend to cost around $2000 each, and that’s just one way. They give you a companion ticket worth $1750 when you book your first flight, to soften the blow. If you don’t have an iPhone you can just go to the web site.